Merge remote-tracking branch 'remotes/borntraeger/tags/s390x-20200310' into staging

Merge remote-tracking branch 'remotes/borntraeger/tags/s390x-20200310' into staging

s390x/ipl: Fixes for ipl and bios

- provide a pointer to the loadparm. This fixes crashes in zipl
- do not throw away guest changes of the IPL parameter during reset
- refactor IPLB checks

# gpg: Signature made Tue 10 Mar 2020 14:50:31 GMT
# gpg:                using RSA key 117BBC80B5A61C7C
# gpg: Good signature from "Christian Borntraeger (2nd IBM address) <borntraeger@linux.ibm.com>" [unknown]
# gpg:                 aka "Christian Borntraeger (IBM) <borntraeger@de.ibm.com>" [full]
# gpg:                 aka "Christian Borntraeger (kernel.org email address) <borntraeger@kernel.org>" [unknown]
# Primary key fingerprint: F922 9381 A334 08F9 DBAB  FBCA 117B BC80 B5A6 1C7C

* remotes/borntraeger/tags/s390x-20200310:
  s390x: ipl: Consolidate iplb validity check into one function
  s390/ipl: sync back loadparm
  s390x/bios: rebuild s390-ccw.img
  pc-bios: s390x: Save iplb location in lowcore

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>